Eady's (1949) model is used to study the non-geostorphic baroclinic stability problem. Growth rates for various types of perturbations are found as a function of the Richardson number, Ri The results indicate that the conventional baroclinic instabilities dominate if Ri > 0.95; symmetric instabilities dominate if 1/4 Ri > 0.95; and symmetric instabilities dominate if Ri < 1/4. It is suggested that symmetric instabilities may play an important role in the dynamics of the atmospheres of the major planets of the solar system.